Castello di Sassari, Medieval castle in Sassari, Italy

Castello di Sassari is a fortified structure in the city with a trapezoidal shape, five corner towers, and a central tower on its main facade. Deep defensive trenches encircle the building, and the interior contains corridors arranged on two levels with glass-covered sections and multiple entry points.

Built around 1330, during Sassari's two rebellions against the Aragonese Crown, the castle was reused under the city's successive rulers. The 2008 excavations uncovered the ground floor and entrance portal of the Aragonese castle, part of the outer barbican, plus a 15th-century moat reaching almost 9 metres deep beneath today's Piazza Castello. The same digs revealed a medieval prison and a maiolica workshop that had stood beside the castle since the 1500s.

The stone flower uncovered in 2009, a five-petalled fountain fed since 1890 by Sassari's new aqueduct, recalls the medieval Pozzo Regio that writers Enrico Costa and Giovanni Francesco Fara placed near the castle gate of Capo di Villa. In the former prison cells, inmates carved religious and macabre drawings and bas-reliefs into the stone walls.

The visitable section is the 16th-century bastion, the so-called antemurale, reached from Piazza Castello. Inside, corridors on two levels held the cannons aimed at the city. The 15th-century moat under the square garden, nearly 9 metres deep in places, was covered and can be visited from inside the fortress; outside, a metal and glass structure shows part of the monument. The World War II air-raid shelter entrance is closed to the public.

The air-raid shelter uncovered in 2008 runs 150 metres underground, with vaults 4 metres high and galleries 3 metres wide; one branch reaches the Poste building. While digging it, quarrymen broke into the medieval passage that led down to the spring beside the Campanone tower, and that older route is still visible on the modern tunnel's vault.